The program 'dag' you mention has gone through multiple revisions and
is now called 'dot'. I find dot to be really useful.

It is currently part of the graph_viz package which you can find it under:
http:/www.research.att.com:80/sw/tools/reuse/

cartegw@humsci.auburn.edu (Gerald W. Carter) wrote:>> 10 years ago or so, some Bright Dudes at AT&T (Gansner, North, and Vo>> are documented) wrote the "BellDag" program to generate nice pictures>> of DAGs. ...